As regular CFZ-watchers will know, for some time Corinna has been doing a column for Animals & Men and a regular segment on On The Track... particularly about out-of-place birds and rare vagrants. There seem to be more and more bird stories from all over the world hitting the news these days so, to make room for them all - and to give them all equal and worthy coverage - she has set up this new blog to cover all things feathery and Fortean.

Thursday, 16 March 2017

A study of the super-diverse bird
groups, which include Darwin's finches, has found that modular skull parts
helped them adapt to different roles.

Adaptive radiation is the rapid
evolution of many diverse species from a single ancestor. Typically this occurs
in the colonization of island habitats, as a group of birds diversifies to exploit different
ecological niches – the lifestyles, or roles, available within an ecosystem.

Two classic examples of adaptive radiation are
Darwin's finches - a group of species native to the Galapagos Islands which
have different beak shapes depending on whether they feed on seeds, fruits or
insects - and Hawaiian honeycreepers, some of which have long beaks adapted to
feeding on the nectar of different flowers.

Darwin's finches were named after
Charles Darwin, whose study of this group of birds played a central role in his
research into evolution.

Previously, scientists have
analysed the shape of beaks to understand how birds diversify and adapt to
these specialist ecological functions. However, because the beak is integrated
with the rest of the skull, examining beak evolution alone does not provide a
complete picture of how these island birds have achieved such remarkable
diversity.

In a new study, published in
Philosophical Transactions of the Royal Society B, researchers compared the 3-D
structure of the entire skull in Darwin's finches, Hawaiian honeycreepers, and
in their common ancestral group, from which the two diverse groups are
descended.

The authors performed X-ray
microcomputed tomography scans (very fine resolution CAT scans) of hundreds of
cleared and dried bird skeletons and fossils of extinct species to compare the
external and internal structure of their skull.

They found that skull shapes are
much more diverse in Darwin's finches, and especially in Hawaiian
honeycreepers, than in their ancestral group or in non-related groups of other
bird species. This whole-skull variation was greater than the variation
observed from looking at just their beaks. The finding suggests that variation
of the entire skull plays an important role in the adaptive radiation of these
birds.